1. Field of Invention
The present invention relates to methods and fluid compositions for use in the extraction of hydrocarbons such as petroleum or natural gas from geological formations.
2. Description of the Related Art
“Fracking,” short for “fracturing,” is popular term for a collection of related techniques for increasing the permeability of geologic formations including hydrocarbons such as petroleum and natural gas, in order to increase the quantity of material that can be extracted from a given formation. Typically, these techniques involves injecting fracking fluid at high enough pressure into a well for the purpose of causing fractures or cracks in the formation emanating from the well and continuing deep into the formation. These cracks provide channels for the flow of trapped formation fluids such as, for example, gas, oil, water, etc., to the well bore. Fracking is applied to many formations improve the flow from the formation. Fracking is employed for the purpose of restoring or improving the porosity of the formation, and thus the permeability of the formation, by opening up the substrate or formation, so that the desired fluid or product can flow more easily to the well pipe.
Fracking is often accomplished by hydraulic methods, pneumatic methods, or by a combination of these methods. Hydraulic fracking is accomplished by pumping a liquid, usually water, along with “proppants,” such as sand or ceramic materials, and often various chemical additives, into the well, forcing the substrate or formation to expand, and resulting in the creation of cracks or wormholes that facilitate the flow of fluids trapped in the formation to the well pipe. Often the injection material is pumped so fast that substantial hydraulic pressure is realized in the well, and the rate of dissipation is often measured as means of judging effectiveness.
The pneumatic method is similar. Enough pressure is generated by pumping gas into the well to force the surrounding formation to expand, which leads to crack formation and increased porosity, and, if proppants are used, to force the proppants into the cracks and pores to keep or prop them open after the pressure on the well is removed.
The gas employed in pneumatic fracking methods can be carbon dioxide, propane, nitrogen, or another gas. However, some gases, such as carbon dioxide and propane, liquefy at elevated pressures, limiting the pressure excursion on the well.
When nitrogen is used as the fracking gas, it must be pumped very quickly into the well, making it a difficult system to work.
There is a continuing need for improved fracking methods that can be employed to extract mineral resources from geological formations.